ORCID Profile
0000-0002-2014-7582
Current Organisations
Broad Institute
,
Brigham and Women's Hospital
,
Harvard Medical School
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: MDPI AG
Date: 04-04-2020
DOI: 10.3390/NU12040999
Abstract: Recent studies indicate that the timing of food intake can significantly affect metabolism and weight management. Workers operating at atypical times of the 24-h day are at risk of disturbed feeding patterns. Given the increased risk of weight gain, obesity and metabolic syndrome in shift working populations, further research is required to understand whether their eating behavior could contribute to these increased metabolic risks. The objective of this study was to characterize the dietary patterns of police officers across different types of shifts in their natural environments. Thirty-one police officers (six women aged 32.1 ± 5.4 years, mean ± SD) from the province of Quebec, Canada, participated in a 28- to 35-day study, comprising 9- to 12-h morning, evening, and night shifts alternating with rest days. Sleep and work patterns were recorded with actigraphy and diaries. For at least 24 h during each type of work day and rest day, participants logged nutrient intake by timest ed photographs on smartphones. Macronutrient composition and caloric content were estimated by registered dieticians using the Nutrition Data System for Research database. Data were analyzed with linear mixed effects models and circular ANOVA. More calories were consumed relative to in idual metabolic requirements on rest days than both evening- and night-shift days (p = 0.001), largely sourced from increased fat (p = 0.004) and carbohydrate (trend, p = 0.064) intake. Regardless, the proportions of calories from carbohydrates, fat, and protein did not differ significantly between days. More calories were consumed during the night, between 2300 h and 0600 h, on night-shift days than any other days (p 0.001). Caloric intake occurred significantly later for night-shift days (2308 h ± 0114 h, circular mean ± SD) than for rest days (1525 h ± 0029 h p 0.01) and was dispersed across a longer eating window (13.9 h ± 3.1 h vs. 11.3 h ± 1.8 h, mean ± SD). As macronutrient proportions were similar and caloric intake was lower, the finding of later meals times on night-shift days versus rest days is consistent with emerging hypotheses that implicate the biological timing of food intake—rather than its quantity or composition—as the differentiating dietary factor in shift worker health.
Publisher: Wiley
Date: 10-03-2022
DOI: 10.1111/JPI.12791
Abstract: The daily rhythm of plasma melatonin concentrations is typically unimodal, with one broad peak during the circadian night and near‐undetectable levels during the circadian day. Light at night acutely suppresses melatonin secretion and phase shifts its endogenous circadian rhythm. In contrast, exposure to darkness during the circadian day has not generally been reported to increase circulating melatonin concentrations acutely. Here, in a highly‐controlled simulated night shift protocol with 12‐h inverted behavioral/environmental cycles, we unexpectedly found that circulating melatonin levels were significantly increased during daytime sleep ( p .0001). This resulted in a secondary melatonin peak during the circadian day in addition to the primary peak during the circadian night, when sleep occurred during the circadian day following an overnight shift. This distinctive diurnal melatonin rhythm with antiphasic peaks could not be readily anticipated from the behavioral/environmental factors in the protocol (e.g., light exposure, posture, diet, activity) or from current mathematical model simulations of circadian pacemaker output. The observation, therefore, challenges our current understanding of underlying physiological mechanisms that regulate melatonin secretion. Interestingly, the increase in melatonin concentration observed during daytime sleep was positively correlated with the change in timing of melatonin nighttime peak ( p = .002), but not with the degree of light‐induced melatonin suppression during nighttime wakefulness ( p = .92). Both the increase in daytime melatonin concentrations and the change in the timing of the nighttime peak became larger after repeated exposure to simulated night shifts ( p = .002 and p = .006, respectively). Furthermore, we found that melatonin secretion during daytime sleep was positively associated with an increase in 24‐h glucose and insulin levels during the night shift protocol ( p = .014 and p = .027, respectively). Future studies are needed to elucidate the key factor(s) driving the unexpected daytime melatonin secretion and the melatonin rhythm with antiphasic peaks during shifted sleep/wake schedules, the underlying mechanisms of their relationship with glucose metabolism, and the relevance for diabetes risk among shift workers.
Publisher: Springer Science and Business Media LLC
Date: 29-03-2019
DOI: 10.1038/S41598-019-41712-1
Abstract: The PERIOD2 ( PER2 ) gene is a core molecular component of the circadian clock and plays an important role in the generation and maintenance of daily rhythms. Rs35333999, a missense variant of PER2 common in European populations, has been shown to associate with later chronotype. Chronotype relates to the timing of biological and behavioral activities, including when we sleep, eat, and exercise, and later chronotype is associated with longer intrinsic circadian period (cycle length), a fundamental property of the circadian system. Thus, we tested whether this PER2 variant was associated with circadian period and found significant associations with longer intrinsic circadian period as measured under forced desynchrony protocols, the ‘gold standard’ for intrinsic circadian period assessment. Minor allele (T) carriers exhibited significantly longer circadian periods when determinations were based on either core body temperature or plasma melatonin measurements, as compared to non-carriers (by 12 and 11 min, respectively accounting for ~7% of inter-in idual variance). These findings provide a possible underlying biological mechanism for inter-in idual differences in chronotype, and support the central role of PER2 in the human circadian timing system.
Publisher: Informa UK Limited
Date: 18-04-2016
Publisher: Springer Science and Business Media LLC
Date: 25-02-2019
Publisher: Oxford University Press (OUP)
Date: 2020
DOI: 10.1093/SLEEP/ZSZ194
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2021
DOI: 10.1161/STROKEAHA.120.031742
Abstract: Circadian biology modulates almost all aspects of mammalian physiology, disease, and response to therapies. Emerging data suggest that circadian biology may significantly affect the mechanisms of susceptibility, injury, recovery, and the response to therapy in stroke. In this review erspective, we survey the accumulating literature and attempt to connect molecular, cellular, and physiological pathways in circadian biology to clinical consequences in stroke. Accounting for the complex and multifactorial effects of circadian rhythm may improve translational opportunities for stroke diagnostics and therapeutics.
Publisher: Elsevier BV
Date: 11-2017
Publisher: Wiley
Date: 29-06-2022
DOI: 10.1002/OBY.23451
Abstract: Later circadian timing of energy intake is associated with higher body fat percentage. Current methods for obtaining accurate circadian timing are labor‐ and cost‐intensive, limiting practical application of this relationship. This study investigated whether the timing of energy intake relative to a mathematically modeled circadian time, derived from easily collected ambulatory data, would differ between participants with a lean or overweight/obesity body fat percentage. Participants ( N = 87) wore a light‐ and activity‐measuring device (actigraph) throughout a cross‐sectional 30‐day study. For 7 consecutive days within these 30 days, participants used a time‐st ed‐picture phone application to record energy intake. Body fat percentage was recorded. Circadian time was defined using melatonin onset from in‐laboratory collected repeat saliva s ling or using light and activity or activity data alone entered into a mathematical model. Participants with overweight/obesity body fat percentages ate 50% of their daily calories significantly closer to model‐predicted melatonin onset from light and activity data (0.61 hours closer) or activity data alone (0.86 hours closer both log‐rank p 0.05). Use of mathematically modeled circadian timing resulted in similar relationships between the timing of energy intake and body composition as that observed using in‐laboratory collected metrics. These findings may facilitate use of circadian timing in time‐based interventions.
Publisher: Proceedings of the National Academy of Sciences
Date: 17-11-2014
Abstract: Although major research efforts have focused on how specific components of foodstuffs affect health, relatively little is known about a more fundamental aspect of diet, the frequency and circadian timing of meals, and potential benefits of intermittent periods with no or very low energy intakes. The most common eating pattern in modern societies, three meals plus snacks every day, is abnormal from an evolutionary perspective. Emerging findings from studies of animal models and human subjects suggest that intermittent energy restriction periods of as little as 16 h can improve health indicators and counteract disease processes. The mechanisms involve a metabolic shift to fat metabolism and ketone production, and stimulation of adaptive cellular stress responses that prevent and repair molecular damage. As data on the optimal frequency and timing of meals crystalizes, it will be critical to develop strategies to incorporate those eating patterns into health care policy and practice, and the lifestyles of the population.
Publisher: MDPI AG
Date: 11-03-2019
DOI: 10.3390/NU11030587
Abstract: The timing of caloric intake is a risk factor for excess weight and disease. Growing evidence suggests, however, that the impact of caloric consumption on metabolic health depends on its circadian phase, not clock hour. The objective of the current study was to identify how in iduals consume calories and macronutrients relative to circadian phase in real-world settings. Young adults (n = 106 aged 19 ± 1 years 45 females) photographically recorded the timing and content of all calories for seven consecutive days using a smartphone application during a 30-day study. Circadian phase was determined from in-laboratory assessment of dim-light melatonin onset (DLMO). Meals were assigned a circadian phase relative to each participant’s DLMO (0°, ~23:17 h) and binned into 60° bins. Lean (n = 68 15 females) and non-lean (n = 38, 30 females) body composition was determined via bioelectrical impedance. The DLMO time range was ~10 h, allowing separation of clock time and circadian phase. Eating occurred at all circadian phases, with significant circadian rhythmicity (p 0.0001) and highest caloric intake at ~300° (~1900 h). The non-lean group ate 8% more of their daily calories at an evening circadian phase (300°) than the lean group (p = 0.007). Consumption of carbohydrates and proteins followed circadian patterns (p 0.0001) and non-lean participants ate 13% more carbohydrates at 240° (~1500 h) than the lean group (p = 0.004). There were no significant differences when caloric intake was referenced to local clock time or sleep onset time (p 0.05). Interventions targeting the circadian timing of calories and macronutrients for weight management should be tested.
Publisher: Proceedings of the National Academy of Sciences
Date: 07-09-2021
Abstract: For centuries, it has been recognized that asthma severity shows a daily rhythm, with the worst symptoms at night. However, it is unclear to what degree this is driven by everyday behaviors, such as sleep, physical activity, and body posture changes, versus intrinsic rhythms generated by the internal body clock (i.e., the circadian system). To distinguish the contribution of the circadian system, patients with asthma underwent two complementary gold-standard circadian protocols: a constant routine and a forced desynchrony protocol. These highly standardized protocols revealed that the endogenous circadian system plays a significant role in modulating pulmonary function and asthma severity independent of sleep and other daily behavioral or environmental cycles. Moreover, these circadian influences summate with daily behavioral and environmental effects to drive asthma to be worst at night.
Publisher: American Diabetes Association
Date: 16-02-2016
DOI: 10.2337/DB15-0999
Abstract: The risk of type 2 diabetes (T2D) is increased by abnormalities in sleep quantity and quality, circadian alignment, and melatonin regulation. A common genetic variant in a receptor for the circadian-regulated hormone melatonin (MTNR1B) is associated with increased fasting blood glucose and risk of T2D, but whether sleep or circadian disruption mediates this risk is unknown. We aimed to test if MTNR1B diabetes risk variant rs10830963 associates with measures of sleep or circadian physiology in intensive in-laboratory protocols (n = 58–96) or cross-sectional studies with sleep quantity and quality and timing measures from self-report (n = 4,307–10,332), actigraphy (n = 1,513), or polysomnography (n = 3,021). In the in-laboratory studies, we found a significant association with a substantially longer duration of elevated melatonin levels (41 min) and delayed circadian phase of dim-light melatonin offset (1.37 h), partially mediated through delayed offset of melatonin synthesis. Furthermore, increased T2D risk in MTNR1B risk allele carriers was more pronounced in early risers versus late risers as determined by 7 days of actigraphy. Our results provide the surprising insight that the MTNR1B risk allele influences dynamics of melatonin secretion, generating a novel hypothesis that the MTNR1B risk allele may extend the duration of endogenous melatonin production later into the morning and that early waking may magnify the diabetes risk conferred by the risk allele.
No related grants have been discovered for Frank Scheer.